采用分子动力学方法模拟了金刚石压头压入Fe基体的纳米压痕全过程.研究了加载和卸载时基体的原子组态、载荷—位移曲线以及位错的发射和变化.分析了基体的塑性形变机理.发现压入深度为0.69 nm时出现位错.随压入深度的增加位错长大成环,基体塑性形变加剧.卸载过程中位错环不断减小,当压头恢复到起始位置后,基体中心残留有位错环,产生了永久塑性形变,位错环的存在是基体产生永久塑性形变的关键因素. Molecular dynamics simulation was used to simulate the whole process of nanoindentation of Fe matrix by pressing indenter. The atomic configuration, load-displacement curve and dislocation emission and change of matrix during loading and unloading were studied. The plasticity Deformation mechanism was found when the depth of 0.69 nm into the dislocations.With increasing the depth of indentation grew dislocations grew, the plastic deformation of the matrix aggravate.Disload ring dislocation process continues to decrease, when the pressure head to return to the starting position After that, the dislocation ring remains in the center of the matrix, resulting in permanent plastic deformation. The existence of dislocation loops is the key factor for the permanent plastic deformation of the matrix.